[brudgers]

This morning I listened to the latter part of Lecture 2B:

  (define (cons x y)
     (lambda (m)
        (cond
           ((= m 0) x)
           ((= m 1) y))))

  (define (car z) (z 0))
  (define (cdr z) (z 1))

As Ableson says, it's made of air.

SICP is not a functional programming course - changing values and creating state comes in Chapter 3 [2nd Edition]. It is a course in the creative use of wishful thinking.